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K Unsicker

Publications and source records attributed to K Unsicker.

At least 109 records · Page 6Linked to original sources
PubMed1995

Bovine chromaffin cells release a transforming growth factor-beta-like molecule contained within chromaffin granules.

Bovine chromaffin cells contain within their storage vesicles and release upon cholinergic stimulation a complex mixture of proteins and peptides. We present data suggesting that one of these proteins resembles transforming growth factor (TGF)-beta in terms of its biological activity. The assay used to assess the activity of TGF-beta is based on cells transfected with a plasminogen activator inhibitor-1 promoter-luciferase construct. The assay is highly specific in detecting TGF-beta 1, -beta 2, and -beta 3 but does not detect several cytokines and growth factors, such as fibroblast growth factor-2, transforming growth factor-alpha, platelet-derived growth factor-AB, insulin-like growth factor-1, or neurotrophin-3 or -4. Moreover, we show that this assay does not detect a wide range of TGF-beta superfamily members (activin A, bone morphogenetic protein-2, -4, -6, and -7, growth/differentiation factor-5, and glial cell line-derived neurotrophic factor). Chromaffin granules contain approximately 1 ng of TGF-beta/10 mg of protein. The biological activity elicited by the chromaffin granule component can be neutralized by using an antibody against TGF-beta 1/beta 2/beta 3. TGF-beta is releasable from cultured chromaffin cells stimulated with the cholinergic agonist carbachol (10(-5) M). These data suggest that TGF-beta is stored in chromaffin granules and can be released by exocytosis.

Animals↗
PubMed1995

Development of mesencephalic dopaminergic neurons and the transforming growth factor-beta superfamily.

Transforming growth factors beta (TGF-beta s) represent a family of multifunctional cytokines affecting growth and differentiation of a large variety of cell types. Several members of this family, as e.g. TGF-beta 2 and -beta 3 as well as glial cell line-derived neurotrophic factor (GDNF), have recently been shown to be expressed in the developing and adult brain. Their neural functions are therefore in the focus of current research. The present review summarizes the evidence concerning their expression in the mammalian midbrain and their functions on developing dopaminergic neurons. Such functions include promotion of survival and protection against N-methyl-4-phenylpyridinium ion (MPP+) toxicity. In contrast to many other cytokines affecting these neurons the mechanism of action of the TGF-beta s does not involve cell proliferation or delivery of growth factors from astroglial cells.

Animals↗
PubMed1994

GDNF is expressed in two forms in many tissues outside the CNS.

A recently cloned neurotrophic factor, Glial Cell Line-Derived Neurotrophic Factor (GDNF), has been implicated in the survival and morphological and functional differentiation of midbrain dopaminergic neurones in vitro. GDNF has therefore been proposed as a factor which may have utility in the treatment of Parkinson's disease. In the present study, we have used RT-PCR to analyse the distribution of GDNF mRNA throughout the newborn rat (P0). We show that GDNF transcripts are present in kidney, lung, bone, heart, liver, spleen, sciatic nerve and blood. Two separate GDNF transcripts are present in different ratios in each tissue investigated. Sequence analysis of both these mRNA species revealed that the shorter transcript (sGDNF) contains a deletion of 78 bp in comparison to the published sequence for GDNF. We speculate that this shorter mRNA arose due to alternative splicing.

Amino Acid Sequence↗
PubMed1994

Presence and regulation of transforming growth factor beta mRNA and protein in the normal and lesioned rat sciatic nerve.

The transforming growth factors beta (TGF-beta), a family of regulatory polypeptides, are involved in numerous vital processes including inflammation and wound healing. Since repair of a peripheral nerve lesion includes a series of well-defined steps of cellular actions possibly controlled by TGF-beta s, and since TGF-beta mRNA and immunoreactivity have been found in the normal peripheral nerve, we have examined in the lesioned peripheral nerve. Sciatic nerves of adult rats were either crushed (allowing axonal regeneration) or transfected (to prevent axonal regeneration and to induce Wallerian degeneration in the distal stump). After intervals of 6 hours, 2 and 6 days post-lesion, the rats were sacrificed and each nerve was cut into four segments, two proximal and two distal to the lesion site. TGF-beta 1-3 mRNA were determined for each segment. We demonstrate that TGF-beta 1 mRNA levels are higher than those of TGF-beta 3; the amplitude of mRNA regulation depends on time, type of lesion and localization relative to the lesion site. TGF-beta 2 mRNA could not be detected. For TGF-beta 1-3 immunocytochemistry, animals were sacrificed 12, 24, 48, 72 hours and 7 and 14 days after surgery. TGF-beta immunoreactivity (IR) was observed for all isoforms in lesioned and unlesioned nerves. In the segment directly adjacent to the lesion at its proximal side, an increase of TGF-beta-IR became apparent as soon as 12 hours after surgery; it remained elevated during the whole period observed in both models. In the segment adjoining the distal side of the lesion, an increase of TGF-beta-IR was observed after 48 hours, which was still present after 14 days. At day 7 after crush or transection, an increase of TGF-beta-IR was detected in the most distal segments, which reached its highest levels at the end of our observation period. Our results suggest that the presence of axonal contact might induce an enhancement of TGF-beta expression by Schwann cells in the distal stump of a lesioned and regenerating peripheral nerve. Since we demonstrate an increase of TGF-beta mRNA and protein expression also in the distal stump of transected nerves where Schwann cells are not able to contact sprouting axons from the proximal part, other regulatory pathways must exist. The acquisition of a "reactive" Schwann cell phenotype after peripheral nerve lesion might involve an upregulation of TGF-beta expression.

Animals↗
PubMed1994

Cell density and exogenous CNTF affect CNTF mRNA levels in glial cell cultures.

Regulation of CNTF mRNA was investigated in primary cortical astrocytes cultured from newborn rats and in C6 glioma cells. Northern blot analysis indicated that semi-confluent astrocyte cell cultures. CNTF added to confluent astrocyte cultures down-regulated CNTF message in a dose-dependent fashion. In contrast, when CNTF was given to semi-confluent astrocyte cultures the level of CNTF mRNA was up-regulated. C6 glioma cells also showed a cell density-dependent expression of CNTF: cells from confluent cultures expressed detectable amounts of CNTF mRNA whereas those from semi-confluent cultures did not. Thus, CNTF mRNA expression by astroglial and glioma cells is regulated by cell contact and exogenous CNTF in vitro.

Animals↗
PubMed1994

FGF-2 in the MPTP model of Parkinson's disease: effects on astroglial cells.

Fibroblast growth factor (FGF) is synthesized and stored by astroglial cells and regulates their proliferation and differentiation in vitro. Its implication in the transformation of quiescent astrocytes into reactive astroglia has been discussed. Using a mouse model of Parkinson's disease, in which FGF-2 has been shown to exert marked neuroprotection of nigrostriatal dopaminergic neurons, we have studied striatal levels of glial fibrillary acidic protein (GFAP), an established marker for astrocytes, and the distribution and morphologies of GFAP-immunoreactive cells following treatments with the neurotoxic drug 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), the growth factor FGF-2, and the non-trophic control protein cytochrome C (cyt C). Systemic injections of MPTP (30 mg/kg) on 3 consecutive days, which we have previously shown to cause profound and long-lasting damage to the nigrostriatal system, induced an approximate 20% transient increase in striatal GFAP, determined by enzyme-linked immunosorbent assay (ELISA), 1 day after the final MPTP injection (= day 4), with subsequent normalization at day 7, which lasted until the end of the experiment (day 18). Morphologically, MPTP elicited a marked increase in number, size, arborization, and stainability of GFAP-immunoreactive cells at day 4 in a striatal area adjacent to the corpus callosum, which was evaluated throughout all experiments. Even on day 18, astrocytes were still apparently larger and more branched than in unlesioned controls. Administration of 4 micrograms of either FGF-2 or cyt C (soaked into a piece of Gelfoam unilaterally to the right striatum in either MPTP- or saline-injected controls) increased striatal GFAP levels bilaterally about 2- to 2.5-fold at 14 days, when FGF-2 showed marked protection of dopaminergic parameters. Likewise, GFAP immunocytochemistry revealed increased numbers of intensely immunoreactive astrocytes under any experimental situation. Differences in the morphologies of astrocytes in FGF-2- and cyt C-treated animals were very subtle and only noted at greater distances away from the site of application of the factors. We conclude that FGF-2, a potent neurotrophic factor for the neurotoxically lesioned nigrostriatal system, does not cause a marked astrogliotic reaction, which might be expected from previous in vitro and in vivo studies in other neural systems. This may limit concerns regarding potential applicability of FGF-2 to the parkinsonian striatum.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1994

Trophic factors from chromaffin granules promote survival of peripheral and central nervous system neurons.

Chromaffin cells of the adrenal medulla were used to study the release of neurotrophic factors operationally defined by their capacity to promote the in vitro survival of embryonic neurons from the peripheral and central nervous system. Chromaffin cells are closely related to sympathetic neurons in terms of their transmitters and specific proteins and, like sympathetic neurons, receive preganglionic cholinergic, aminergic and peptidergic neuronal inputs. The issue of whether chromaffin cells store and secrete neurotrophic factors is therefore pertinent to the question whether trophic mechanisms may be involved in neuronal interactions and what modes of secretion are employed to liberate neurotrophic factors from neurons. Cell culture media conditioned by purified bovine chromaffin cells supported several neuron populations in vitro. Stimulation of the chromaffin cells with the cholinergic agonist carbachol (10(-4) M) increased in parallel the output of neurotrophic factor activity (assayed on chick ciliary ganglionic neurons) as well as two components specifically located in chromaffin granules, chromogranin A and catecholamines. The release of all three components was partially blocked by the Ca2+ channel blocker verapamil (10(-5) M), suggesting co-storage and -release of neurotrophic factors, chromogranin A and catecholamines in/from chromaffin granules. Neurotrophic factor activity for ciliary ganglionic neurons accumulating in the medium of unstimulated chromaffin cells decreased with time, and so did catecholamines. In contrast, amounts of neurotrophic factors and catecholamines released by challenging cells with carbachol did not significantly decline up to 62 h. The neurotrophic factor activity tested on chick ciliary, sensory and spinal cord neurons as well as on rat hippocampal neurons was heat- and trypsin-labile and could not be blocked by polyclonal antibodies against bovine nerve growth factor and the chromogranin A, B, and C. Defined fragments of chromogranin A and pancreastatin were devoid of neurotrophic activity. Our results suggest the presence of one or several neurotrophic factors in chromaffin granules, which can be released by exocytosis and may be potentially relevant for the maintenance of neurons innervating the adrenal medulla.

Adrenal Medulla↗
PubMed1994

Transforming growth factor-beta promotes survival of midbrain dopaminergic neurons and protects them against N-methyl-4-phenylpyridinium ion toxicity.

Transforming growth factors beta are multifunctional proteins and regulators of cell proliferation and differentiation. Transforming growth factor-beta s have the capacity to rescue adult neurons from ischemia- and glutamate-induced cell death and are prominent in the embryonic and adult brain including striatum and substantia nigra. In the present study we show that transforming growth factors-beta 1, -2, and -3 promote, in a dose-dependent fashion, in vitro survival of tyrosine hydroxylase-immunoreactive dopaminergic neurons isolated from the embryonic rat mesencephalon floor. The magnitude of the effect, which was half-maximal at a concentration of 20 pM, was identical for all three transforming growth factor-isoforms and matched that of fibroblast growth factor-2. Unlike fibroblast growth factor-2, however, transforming growth factor-beta s did not increase numbers of astroglial cells visualized by using antibodies to glial fibrillary acidic protein, and had no effect on cell proliferation monitored by incorporation of BrdUrd. Transforming growth factor-beta s were significantly more potent than fibroblast growth factor-2 in protecting dopaminergic neurons against N-methyl-4-phenylpyridinium ion toxicity. RT-PCR analysis indicated that the effect of transforming growth factor-beta s is not mediated by glial cell-derived neurotrophic factor, which was not detectable in cultures at various time points. On the other hand transforming growth factor-beta 2 mRNA could be detected in freshly isolated and cultured mesencephalic cells, and its immunoreactivity has also been demonstrated in the embryonic day 14 mesencephalon floor. We conclude that transforming growth factor-beta has trophic and protective effects on developing dopaminergic neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-4-phenylpyridinium↗
PubMed1994

Interleukin-1 beta and interferon gamma interact with fibroblast growth factor-2 in the control of neuroblastoma cell proliferation and differentiation.

Based on our previous observations that neuroblastoma (NB) cells express fibroblast growth factor-2 (FGF-2; basic FGF) and respond to it [Janet T. et al. (submitted); Wewetzer K. et al. (1993) J. Neurosci. Res. 36, 209-215), we attempted to find to what extent selected cytokines [interleukin (IL)-1 beta and interferon gamma (IFN gamma)] may modulate FGF-mediated proliferative activity and differentiation. The NB cell lines IMR-32, SH-SY5Y, GIMEN and LAN-1 and colorimetric assays were used for the determination of cell numbers. IL-1 beta (and several other ILs, including IL-1 alpha, -2, -3, and 6) per se did not affect proliferation of any cell line studied. IFN gamma inhibited growth of GIMEN and LAN-1 cells, but was uneffective on IMR-32 and SH-SY5Y cells. FGF-2 was antimitogenic for GIMEN cells. IFN gamma reversed and IL-1 beta enhanced this antimitogenic effect of FGF-2. FGF-2 per se did not affect LAN-1 cells and did not modulate the growth inhibitory actions of IFN gamma on these cells. FGF-2 induced proliferation of IMR-32 and SH-SY5Y cells. This effect was not modulated by IFN gamma or IL-1 beta. These results suggest a heterogeneous response pattern of human NB cell lines towards the cytokines studied and complex interactions of FGF-2, IL-1 beta and IFN gamma.

Cell Differentiation↗
PubMed1994

Growth factors in Parkinson's disease.

The etiology of Parkinson's disease, one of the most frequent neurodegenerative disorders in human, is unknown. New hopes concerning satisfactory therapies include transplants of autologous adrenal medullary chromaffin tissue, fetal mesencephalic dopaminergic neurons, and local application of growth factors with a neurotrophic capacity. A large body of evidence supports the notion that neurons require trophic support not only during a limited period of ontogenesis, but during their whole lifespan. Relevant molecules promote survival, transmitter synthesis and other differentiated properties, and become crucially important when a neuron is metabolically or toxically impaired. Several molecules, most of which occur in the striatum and the substantia nigra, have been identified that protect lesioned dopaminergic nigrostriatal neurons in culture or in animal models of Parkinson's disease. These include members of the neurotrophin, fibroblast growth factor, and insulin-like growth factor families as well as epidermal growth factor/transforming growth factor alpha, interleukins and ciliary neurotrophic factor. Whether their effects are merely pharmacological, or reflect a physiological role in the nigrostriatal system, is unclear as yet. This article reviews experiments that document the trophic effects of these factors on dopaminergic neurons and discusses their possible physiological and therapeutic relevance.

Animals↗
PubMed1994

HOE-BAY 946 has distinct effects on spontaneous and FGF induced proliferation of epithelial and neuroblastoma cell lines.

We have studied in vitro the effects of HOE-BAY 946, a specific inhibitor of tyrosine kinase C, on spontaneous and basic FGF-induced proliferation of the epithelial cell lines A549 and HELA as well as the neuroblastoma cell line SY5Y using a fully automated colorimetric assay for determinations of cell numbers. HOE-BAY suppressed spontaneous proliferation of the epithelial lines, but not the neuroblastoma line, both in the presence and absence of serum. In contrast, the drug completely abolished the mitogenic effect of basic FGF on all cell lines. This suggests an involvement of a tyrosine kinase C activity in the transduction of the FGF signal both in the epithelial and neuroblastoma lines. Since the action of FGF on non-transformed neuronal cells is accompanied by a down-regulation of kinase C, and kinase C activation blocks the FGF effects, our data indicate that differentiative and mitogenic effects of FGF on neuronal cells may employ different transduction mechanisms.

Analysis of Variance↗
PubMed1993

Synthesis and release of the beta-amyloid precursor protein by bovine chromaffin cells.

Production of the beta-amyloid precursor protein (beta APP) by bovine adrenal chromaffin cells was investigated by polymerase chain reaction (PCR) and by immunoblot. Chromaffin cells were found to synthesize forms of beta APP similar to those found in the rat PC12 pheochromocytoma cell line and to secrete these constitutively into their culture medium. Release of beta APP could be enhanced by stimulation with phorbol ester but not by cholinergic stimulation of secretion. The fact that normal chromaffin cells produce beta APP suggests that beta APP has some (as yet undermined) function in the adrenal medulla in vivo.

Amyloid beta-Protein Precursor↗
PubMed1993

Induction of phosphatidic acid by fibroblast growth factor in cultured baby hamster kidney fibroblasts.

Basic fibroblast growth factor (bFGF/FGF-2) is a strong mitogenic inducer of cultured baby hamster kidney (BHK) cells. When cultured BHK cells were stimulated with FGF-2, phosphatidic acid (PA) was induced within 2 min, peaked at 5 min and gradually decreased. Phospholipase D (PLD) was also mitogenic for cultured BHK cells and this effect was mediated via PA. The possibility that PA induction by FGF-2 is an essential signaling step for BHK cell proliferation is discussed.

Animals↗
PubMed1993

Cell blotting and isoelectric focusing of neuroblastoma-derived heparin-binding neurotrophic activities: detection of basic fibroblast growth factor protein and mRNA.

Neuroblastoma cells have been shown to contain growth factors, which may be involved in the regulation of cell proliferation and/or differentiation. We have examined whether human IMR-32 neuroblastoma cells store factors with a capacity to promote neuron survival and differentiation. Heparin affinity chromatography, cell blotting, and isoelectric focusing of IMR-32 cell extracts revealed multiple neurotrophic activities at molecular weights of 16.8, 24.1, 39.0, 45.3, 52.3 and isoelectric points of 4.0, 5.0, 8.3, 9.0. Immunocytochemistry, immunoblotting, and radio-immunoassay with specific antibodies suggests that one neurotrophic activity is immunologically identical with basic fibroblast growth factor (bFGF). This assumption is supported by Northern blot analysis, which shows a 6.0 kb bFGF transcript.

Animals↗
PubMed1993

FGF-2 modulates dopamine and dopamine-related striatal transmitter systems in the intact and MPTP-lesioned mouse.

Following a previous study in which we showed ameliorative effects of basic fibroblast growth factor (FGF-2) locally applied to the nigrostriatal system in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mice, we investigated FGF-2 actions at different time intervals after the lesion and effects on non-dopaminergic striatal transmitter systems. A triple intraperitoneal injection of 30 mg/kg MPTP at 24 h intervals caused a reduction of striatal dopamine to 23% of control levels that lasted for at least 4 weeks. Four micrograms FGF-2 soaked into gel foam and placed onto the right striatum partially and bilaterally restored dopamine levels and tyrosine hydroxylase activity after 2 weeks, when the treatment started simultaneously or 1 day after the toxin lesion. FGF-2 was ineffective, if administration commenced with a delay of 7 days. Striatal neurotransmitters that are known to be linked to the dopaminergic system were also altered by the MPTP treatment. GABA was significantly increased, while somatostatin levels were reduced. Upon FGF-2 administration both GABA and somatostatin levels were partially normalized. Our data are consistent with the notion that FGF-2 protects and rescues acutely and subacutely MPTP-lesioned nigrostriatal neurons and that its effects must be mainly indirect. Likewise, positive effects of FGF-2 on non-dopaminergic neurons may be due to the partial restoration of striatal dopamine.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

FGF-2-mediated protection of cultured mesencephalic dopaminergic neurons against MPTP and MPP+: specificity and impact of culture conditions, non-dopaminergic neurons, and astroglial cells.

The protective role of basic fibroblast growth factor (FGF-2) for 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- and methylpyridiniumion (MPP+)-lesioned dopaminergic (DAergic) nigrostriatal neurons was studied, using dissociated cell cultures of embryonic day (E) 14 rat mesencephalon. Cells were grown in different culture media and received FGF-2 (5 ng/ml) and/or the toxins (5 microM) at various schedules, but were consistently allowed to differentiate for 3 days prior to becoming exposed to the toxin. Survival of tyrosine hydroxylase (TH)-immunoreactive cells at 7 days was only markedly impaired by MPTP, if horse serum (HS) or bovine serum albumin (BSA) were omitted from the culture medium. FGF-2 increased the number of TH-immunoreactive cells, and this increase was not diminished by MPTP under any culture condition. Uptake of 3H-DA was significantly reduced by MPTP in HS- and BSA-containing, but not in protein-less cultures. A protective effect by FGF-2 was only seen in the presence of BSA. MPP+ caused a more pronounced reduction in 3H-DA uptake than MPTP, and this effect was partially reversed by the addition of FGF-2, unless cultures contained HS. Neurofilament protein (NF), and indirect measure for the total number of neurons present in the cultures, was not significantly reduced by MPTP or MPP+ corroborating the specificity of the toxin for DAergic neurons, which constitute only a minor fraction in these cultures. In line with the wide spectrum of target neurons of FGF-2, this factor significantly increased NF contents under any culture condition. Quantification of the amounts of glial fibrillary acidic protein (GFAP) revealed stimulatory effects of FGF-2 (2.5- to 4-fold) and at least 10-fold higher levels in the presence as compared to the absence of HS. These data show that FGF-2 can protect DAergic neurons against MPTP- and MPP(+)-mediated damage. However, the effects of the toxins as well as of FGF-2 are partially dependent on culture conditions. Variations in the effectiveness of toxins and FGF-2 are not overtly related to the total numbers of neurons or astroglial cells, but may reflect culture type-dependent alterations of neuronal and glial metabolism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

The trophic cocktail made by adrenal chromaffin cells.

The beneficial effect of chromaffin cell grafts to the striatum in patients with Morbus Parkinson and in animal models of the disease may be due to liberated growth factors rather than to the relatively small amounts of dopamine released. This overview summarizes the current knowledge concerning synthesis, storage, and release of growth factors and neuropeptides with growth factor-like effects by chromaffin cells. Peptides of interest include several well-established neurotrophic factors, neuropeptides, and cytokines known to stimulate neurotrophic factor levels in a number of neural lesion paradigms, such as fibroblast growth factor-2, transforming growth factors-beta, interleukins, enkephalins, somatostatin, neurotensin, VIP, and biological activities resembling ciliary neurotrophic factor. Fibroblast growth factor-2 has been most extensively studied, and its ameliorative effects on pathological chemical and morphological parameters of the Parkinsonian brain will also be addressed.

Adrenal Glands↗